Actually, rust has been an issue for as long as I can remember and I got my first Hobie in 1976. Most of what we see is not the material breaking down, but a surface contaminant that is rusting off.
There are many grades of stainless. The more carbon in the stainless, the harder it is and less shiny. You see that in cutlery. Stainless is soft and cannot hold an edge. Carbon is stiffer, but discolors.
Most of the rust stains seems to come from fasteners. Carbon tooling leaves residue on the threads. That residue rusts away.
I wrote a FAQ on the subject: http://www.hobiecat.com/community/viewtopic.php?t=1513
We had some bad halyard cable some time back that was something like galvanized steel and not stainless. This was caught very quickly. Maybe that is what some of this was?